U.S. patent number 10,315,405 [Application Number 15/349,349] was granted by the patent office on 2019-06-11 for methods and apparatus for applying protective films.
This patent grant is currently assigned to EXEL INDUSTRIES. The grantee listed for this patent is EXEL INDUSTRIES. Invention is credited to Michael DeFillipi, Vipin Patel.
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United States Patent |
10,315,405 |
DeFillipi , et al. |
June 11, 2019 |
Methods and apparatus for applying protective films
Abstract
An applicator die for creating undivided ribbons of polymeric
film and a method of using the die to apply an emulsified polymeric
material in ribbons to a fully or partially finished surface of an
automobile body. In one application, the ribbon is applied as a
peelable film to an automobile body and in another application, a
ribbon is applied to a rocker panel as an anti-chip coating. For
both applications, the applicator die has an internal gallery and
an outlet slot with flared edge surfaces to emit a laminarized
ribbon of polymer-based material at a distance from the target
surface where the opposite edges of the ribbon have become
essentially parallel.
Inventors: |
DeFillipi; Michael (Plymouth,
MI), Patel; Vipin (Livonia, MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
EXEL INDUSTRIES |
Paris |
N/A |
FR |
|
|
Assignee: |
EXEL INDUSTRIES (Paris,
FR)
|
Family
ID: |
58189882 |
Appl.
No.: |
15/349,349 |
Filed: |
November 11, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170066231 A1 |
Mar 9, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14311533 |
Jun 23, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B05D
5/00 (20130101); B32B 37/0046 (20130101); B32B
37/153 (20130101); B05D 1/26 (20130101); B05C
5/0254 (20130101); B05C 5/0283 (20130101); B05C
5/0216 (20130101); B05D 1/325 (20130101) |
Current International
Class: |
B05D
1/40 (20060101); B32B 37/00 (20060101); B32B
37/15 (20060101); B05D 5/00 (20060101); B05D
1/26 (20060101); B05C 5/02 (20060101); B05D
5/02 (20060101); B05D 1/32 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2289923 |
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Nov 1998 |
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CA |
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102006012373 |
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Jun 2007 |
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DE |
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102010011095 |
|
Oct 2010 |
|
DE |
|
0484980 |
|
May 1992 |
|
EP |
|
1008632 |
|
Jun 2000 |
|
EP |
|
2038211 |
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Jul 1980 |
|
GB |
|
2145640 |
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Apr 1985 |
|
GB |
|
2000260310 |
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Sep 2000 |
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JP |
|
2002066420 |
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Mar 2002 |
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JP |
|
0067915 |
|
Nov 2000 |
|
WO |
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WO-2010073751 |
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Jul 2010 |
|
WO |
|
Other References
Machine translation of Japanese Patent Publication No.
JP-2000260310A, originally published Sep. 2000, 18 pages (Year:
2000). cited by examiner .
Machine translation of Japanese Patent Publication No.
JP-200206420A, originally publshed Mar. 2002, 9 pages (Year: 2002).
cited by examiner.
|
Primary Examiner: Bell; William P
Attorney, Agent or Firm: Young Basile Hanlon &
MacFarlane, P.C.
Parent Case Text
CROSS REFERENCE OF CO-PENDING APPLICATION
This application is a continuation-in-part of U.S. patent
application Ser. No. 14/311,533, filed Jun. 23, 2014, the entire
content of which is incorporated herein in its entirety.
Claims
What is claimed is:
1. A die for extruding a protective film of an undivided polymeric
emulsion having a viscosity in the range of 3000 to about 12,000
centipoise adheringly onto a surface of an article of manufacture
comprising: a die body having an inlet for said emulsion and a flow
passage extending from said inlet to a slot-shaped outlet formed
through an elongate end surface in said die body; said end surface
having a flat linear central expanse terminating in mirror image
uniformly rounded opposite corners each having a respective center
of curvature; a gallery volume formed in and extending across said
passage within said body to receive said emulsion as it flows from
said inlet toward said outlet, said volume having a downstream edge
with 180.degree. rounded opposite ends each having a respective
center of curvature corresponding to the center of curvature of
said end surface corners; and said discharge passage having
outwardly flared opposite side surfaces that extend from respective
opposite tangent points on said rounded ends to respective opposite
rounded corners wherein the degree of outward flare is between 5
and 50 degrees relative to the material flow direction at the
center of said passage whereby the flow rate of said emulsion from
said volume to and through said end surface is substantially the
same across said passage end surface.
2. A die as defined in claim 1 wherein the length of the discharge
outlet from end to end is approximately 85 mm.
3. The die body defined in claim 1 wherein said passage is formed
in part by a shim and said die body is formed in two parts with
said shim located between said two parts and wherein said shim
further defines an upper edge of said gallery volume.
4. A method for adheringly applying ribbons of a protective film of
polymeric material to a surface on an object comprising the steps
of: (a) positioning the extrusion die defined in claim 1 a
predetermined distance from the surface; (b) supplying an
emulsified polymer based material to the die to cause a uniform,
unatomized ribbon of said material to issue from the die at a speed
between about 1500 mm/sec to 2000 mm/sec; (c) moving the die
relative to the surface to cause the issuing ribbon to adheringly
contact the body uniformly to coat the body while maintaining said
predetermined distance; said predetermined distance being such that
edges of the ribbon at said distance are have become essentially
parallel and no part of the die contacts the ribbon portion in
adhered contact with said surface.
5. The method defined in claim 4 wherein the step of moving the die
is carried out in alternatingly reverse-direction and overlapping
strokes.
6. The method defined in claim 4 wherein the material is an aqueous
emulsion of polyvinyl acetate and the applied ribbons are about 200
microns thick over a majority of their width.
7. The method defined in claim 4 wherein the method includes the
further steps of curing the film and, thereafter, peeling the film
from the body.
8. A method of protecting a portion of a painted surface of an
automobile body comprising the steps of: a. providing an uncured
fluidic solution of polyvinyl acetate with a viscosity in the range
of about 7,000 to about 12,000 centipoise to an inlet of an
extrusion die having a flow passage with a flared outlet slot that
is configured to emit an uncured ribbon of said solution with
uniform edge to edge consistency in viscosity and flow rate and an
outwardly lateral flare on both edges of between 5.degree. and
50.degree. ; b. causing said solution to pass through said die
passage to produce said ribbon thereby to cause said ribbon to
expand laterally for a predetermined downstream distance from said
die outlet to a maximum width wherein the edges of said ribbon are
essentially parallel; c. positioning said die at said predetermined
downstream distance from said automobile body surface during
extrusion to cause the ribbon to adheringly contact the surface;
said distance being such that no portion of the die contacts the
ribbon portion adhered to the body surface; d. moving the die
relative to the body surface at a speed which substantially matches
the speed at which the ribbon is emitted from the die outlet slot;
and e. thereafter curing the applied ribbon on the automobile
body.
9. The method described in claim 8 wherein the speed of movement
between the die and the body surface is between about 1,500 and
2,000 mm/second and substantially equals the speed at which the
ribbon is emitted from the die outlet slot.
10. The method of claim 8 wherein the dimension of the slot from
side edge to side edge is approximately 85 mm and thickness of the
extruded film is approximately 0.2 mm.
Description
FIELD OF THE INVENTION
Disclosed herein are methods for protecting fully or partially
finished surfaces of articles of manufacture such as automobiles by
producing and applying a polymeric film to the article wherein the
apparatus used to carry out the methods includes an applicator die
configured to hydraulically deliver a laminarized ribbon of
polymer-based film with controlled width, thickness and edge
characteristics.
BACKGROUND OF THE INVENTION
It is known to protect the painted exterior surfaces of glass and
automobile parts with pre-formed, laminated sheets or sprayed-on
polymeric films for various purposes; e.g., to reduce the
likelihood of damage during shipment, storage and use or to act as
spacers for stacking. There have been numerous problems associated
with the application of such films. Spraying invokes the need to
deal with environmental issues as well as overspray, both in the
air and on parts of the article which are not to be coated. For
non-permanent applications, it is often necessary to use solvents
to remove the film. Lamination involves, first, the extrusion of a
thin sheet of plastic film and, second, the step of joining the
plastic film to a paper backing so it can be rolled up for shipment
or storage. When the time comes to apply the film to, for example,
an automobile body, several laborers are required to unroll the
paper-backed film, lay the film over the automobile, remove the
paper backing, and smooth the film. The result is a peelable film
requiring no solvents or detergents for removal, but the
manufacturing and application processes are labor intensive and,
therefore, creates substantial expense.
It is also known to apply a film or coating of resilient protective
polymeric material such as PVC to the rocker panels and other
locations on automobile bodies to serve as an anti-chip coating.
The coating is typically sprayed onto the vehicle rocker panel
during the painting phase and dried or cured using, for example,
standard paint oven convection heating. This sprayed-on method of
application requires carefully masking of the body of the vehicle
for overspray protection, which is labor-intensive. The masking
must also be removed and disposed of, adding further cost to the
process.
SUMMARY OF THE INVENTION
In general, this document discloses a manner in which large and
small areas of fully or partially finished surfaces of manufactured
products can be temporarily or permanently coated with
polymer-based protective films, which films can be applied by the
controlled hydraulic "extrusion" of a laminarized ribbon of
polymer-based material without atomization and with controlled
width, thickness and edge characteristics. This method can create,
for example, ribbons of polymeric film that have a desired
thickness profile from edge to edge that promotes peelability and
that can be applied extremely close to a part edge or a seam
between adjacent assembled parts without crossing or bridging the
seam. This virtually eliminates the problems associated with prior
art spray methods as well as the labor intensive steps of applying
protectant from a paper backed roll of pre-extruded film. The
method can also be used to apply ribbons of polymeric film for
other purposes.
An aspect of the subject matter described herein is an applicator
die for producing a ribbon or film of fluidized polymeric material
directly onto a surface to be protected without atomization or
other division of the film leaving the die. The applicator die can
be robotically guided and controlled as to spacing from the target
surface to dynamically and consistently lay down a polymeric film
of the desired width, length, thickness and edge characteristics in
a precise fashion, i.e., coming very close to seams and part edges,
and at low labor cost. Although the examples described herein
involve fairly flat surfaces, the applicator can be configured to
conform to curved or complex surfaces. The applicator described
herein may be said to "hydraulically extrude" a film of
laminarized, emulsified polymeric material in a ribbon with such
well controlled edge-to-edge consistency and thickness as to be
suitable for masking as well as protection. A preferred emulsion
thickness for protecting painted auto body surfaces is 200 microns
(wet) with slight beads on the edges to promote peelability. This
is readily distinguished from sound-deadening material which is
generally 2000 or more microns thick and is not peelable. When used
to produce a protective layer for an automobile body, the prior art
steps of pre-extruding and backing a film are eliminated because
the robotic arm guiding the applicator can be indexed to produce
multiple overlapping ribbons that together cover large
uninterrupted areas right up to edges or seams. Moreover, the
applicator hereinafter described in detail can be "ambidextrous" in
that it is capable of producing adjacent parallel ribbons of
plastic film without indexed rotation for reversal; i.e., the
applicator can be reversed in its direction of travel. In addition,
the applicator can be used to apply different materials for
different purposes to horizontal, vertical and inverted surfaces,
whether flat, concave or convex.
Another aspect of the subject matter described herein is the use of
the applicator die described above to apply a protective film of a
polymeric material, such as an aqueous solution of polyvinyl
acetate (PVA), to the fully or partially finished surfaces of an
automobile body or component part therefor. As stated above, this
may be for masking or protection purposes, in which case the film
is temporary and must be peelable. The film is, after curing,
readily and easily peelable without the use of solvents of
detergents in large part because it is of its thickness profile
across its width. For the reasons described above, this process is
highly efficient due in part to the fact that the application of
overlapping polymeric ribbons, applied in a back and forth fashion
to cover large areas, can be carried out simply by indexing the
applicator between parallel rows and without the need to rotate the
applicator 180.degree. for the next run. The applicator can
essentially be moved relative to the application surface at about
the velocity at which the applied material is emitted from the
applicator die. Velocities of about 1500 to 2000 mm/second have
been achieved. However, translation speed will vary from
application to application.
As further described herein, the preferred applicator die comprises
a two-part body with an inlet, an internal gallery, a bottom edge
in which a long, narrow, outlet slot is created by a spacer or shim
placed between the two mirror-image body parts, and the shim
thickness controls the thickness of the film or ribbon to be
extruded. The preferred gallery includes internal grooves in the
two body parts that face each other and run parallel to and
adjacent the bottom edge, although a one-sided groove arrangement,
is also feasible. The gallery groove or grooves create an internal
volume for material received from the inlet and emit or "extrude"
that material through the slot between the facing surfaces of the
two body parts. The shim geometry relative to the gallery groove
has been found to be important in controlling film edge qualities;
i.e., the gallery grooves are radiussed, i.e., 180.degree. rounded
at their ends and the shim is designed with a top edge that lies
along the top edge of a gallery groove and with side edges that
flare out at an angle of about 5.degree. to 50.degree. but
preferably 17.degree. to create a slightly broadening film.
Importantly, the length of the extrusion outlet slot surfaces over
which the film material passes between the gallery slot and the die
exit edge is constant from one edge of the slot to the other and we
have found that this ensures a substantially uniform film flow
velocity across the entire width of the extrusion slot.
For peelable protective film or for masking, a film with a uniform
thickness of 200 microns from edge to edge is preferred. This
results from the shim geometry shown in FIG. 11B and described
below. An exemplary film width is 75-85 mm.
Another aspect of the subject matter disclosed herein is the use of
the aforementioned applicator die in applying an anti-chip coating
to, for example, the rocker panels of an automobile body. In this
case, the material being applied can be an undirected; i.e.,
non-atomized, laminar-flowing ribbon of emulsified polyvinyl
chloride (PVC). In the preferred embodiment, the PVC ribbon is
applied over electro-coat primer previously applied on the rocker
panel but before the application of the paint primer, base color
and clear coat. It has been determined that it is not necessary to
wait for the PVC ribbon to completely dry before the paint primer
is applied; i.e., the subsequent coatings can be applied
"wet-on-wet," greatly reducing production time and totally
eliminating the need for masking and spraying as are required in
the prior art techniques.
Other advantages, features and characteristics of the subject
matter disclosed herein, as well as methods of operation and
functions of the related elements of the structure, and the
combination of parts and economies of manufacture, will become more
apparent upon consideration of the following detailed description
and the appended claims with reference to the accompanying
drawings, the latter being briefly described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
The description herein makes reference to the accompanying drawings
wherein like reference numerals refer to like parts throughout the
several views and wherein:
FIG. 1 is a perspective view of an applicator die as described
herein mounted on a robot arm and used to apply a protective film
to the hood of an automobile;
FIG. 2 is a schematic view of a representative pattern of runs of
the robotically moved applicator die in fully covering an
automobile hood;
FIG. 3 is a plan view of the ribbons laid down by the run pattern
of FIG. 2;
FIG. 4 is a perspective view of another application of the
teachings herein as applied to the use of permanent protective
films on rocker panels;
FIG. 5 is an exploded view of an applicator as described in the
following specification;
FIG. 6 is a sectional view through the application of FIG. 4;
FIGS. 7A, B, C, and D are diagrams of a material ribbon emerging
from applicator dies of different design;
FIG. 8 is a block diagram of one of the methods described
herein;
FIG. 9 is a block diagram of another method;
FIG. 10 is a schematic diagram of a complete system; and
FIGS. 11A and B are full and partial plan views of the shim 26 of
FIG. 5 overlying a die block 26 wherein FIG. 11 B indicates a flow
pattern found to be advantageous.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
Referring to FIG. 1, an applicator die 10 is shown mounted on the
end of an arm 12 of a numerically controlled multi-axis robot 14
capable of moving the applicator die in three-dimensional space as
well as rotating the applicator die about multiple axes. The robot
itself is conventional. The applicator die 10 is shown engaged in a
process of applying 85 mm wide and 200 micron thick ribbons 16, 17
of polymeric film to the hood of an automotive vehicle which has
been painted and essentially fully assembled, ready for shipment to
a dealer. In FIG. 1, a first ribbon 16 has been applied across the
rearmost portion of the hood 18; i.e., the portion closest to the
windshield of the automobile, by moving the robot from right to
left along a slightly curved path as shown in FIG. 1. The robot
then indexed the arm 12 toward the front of the vehicle and is
shown in the process of applying a second ribbon 17 moving from
left to right across the hood 18 as seen in FIG. 1. Each ribbon is
approximately 85 mm wide, and with an overlap with the adjacent
ribbon or ribbons of about 1-7 mm. The preferred thickness profile
for this particular application is uniform from edge to edge at
about 200 microns.
The material being applied is an aqueous solution of polyvinyl
acetate (PVA) at a temperature between about 70.degree. and
120.degree. F. and with a viscosity of about 3000 to 12,000
centipoise. Material is supplied to applicator die 10 under close
temperature and flow rate control conditions via supply conduit 20;
temperature-controlled liquid is supplied via conduit 21. The
velocity of the material ribbon from the applicator can, for
example, be as much as about 2000 mm/second and the robot 14 moves
the applicator die 10 relative to the surface of the hood 18 at
about that same speed. The spacing between the material outlet,
i.e., the bottom edge of the applicator die 10 and the surface of
the hood 18 is about 5 to 15 mm. The ratio of polymer to water in
the applied material in an illustrative case is approximately 50/50
but will vary with the application. These figures are given by way
of example. Robot speed, extrusion rate, spacing and emulsion
ratios can all vary.
Referring now to FIGS. 2 and 3, the complete coverage of the hood
18 is achieved using crosswise movements to produce ribbons 16a,
16b, 16c and 16d in a back-and-forth fashion, the robot serving to
index the applicator forward by just less than the width of the
applied ribbon but without the need to rotate the applicator die 10
through 180.degree. as the applicator die 10 is entirely
ambidextrous; i.e., it has no "forward" side and operates in a
spatial orientation nearly or completely orthogonal to the surface
upon which material is being applied.
As shown in FIGS. 2 and 3, the material is applied to the surface
of the hood in back-and-forth, overlapping ribbons until the
forward-most ribbon 16d is applied at which time the applicator is
rotated 90.degree. and moved along the ribbon 16e to cover the left
edge of the hood and the lateral ribbon ends, as shown in FIG. 2.
The applicator is then moved to the top right portion of the hood,
as shown in FIG. 3 to apply the final ribbon 16f. It will be noted
that material is not applied across vehicle body seams. The pattern
of ribbons in FIGS. 2 and 3 is illustrative only.
Looking now to FIGS. 5 and 6, an applicator die 10 is shown. It is
referred to as an "applicator die" because the film ribbons issued
from it are essentially hydraulically extruded as opposed to
atomized or aerated and sprayed. There is no "spray" of particles
or droplets. The term "hydraulic extrusion" is used herein to mean
a laminarized flow or non-atomized fluid propelled by hydraulic
pressure rather than by air or other compressible propellant. The
applicator die 10 is shown to comprise blocks 23 and 28 which are
machined out of solid stainless steel, for example, about31/2''
long by 2'' high with rounded bottom corners and mitered top
corners for weight reduction. Placed between the two blocks 23 and
28 in the assembled condition is a shim or spacer 26 made of brass,
stainless steel, plastic or other suitable material having locator
holes 52 so that it may be precisely located on guide pins 40 which
are inserted into precisely located holes in the interior surface
41 of the block 23. A fourth element of the applicator die
combination is a valve 30 which helps to produce sharper cutoffs as
hereinafter explained.
Block 23 is thicker than block 28 and includes a threaded material
entry port 22, which extends downwardly to approximately the center
of the block where it communicates with a forwardly directed
passage 32 which, in turn, feeds material into a gallery of
machined grooves comprising diverging legs 34, 36 and a horizontal
cross-groove 38, all of which are of the same depth. A horizontal
groove 50 is formed in the inside surface 31 of block 28 in full
face-to-face registry with groove 38 in block 23 to create a
gallery volume parallel to and adjacent the bottom edge surface of
the die. The spacer 26 fits flush against the inside surface 41 of
the block 23 to cover most of the grooves 34 and 36 of the gallery;
the shim has a lower cutout or "relief" 44 with 15.degree. flared
side edges 46 and 48, which terminate at points TP on the radiused
corner arcs of the die block which is 36 degrees from the vertical
centerline as shown in FIGS. 11A and 11B. The shim provides a gap
between the inside surfaces 41, 31 of blocks 28 and 23,
respectively, of uniform thickness for material to flow downwardly
from the horizontal grooves 38 and 50 and out through the bottom
outlet 58 of the die, as shown in FIGS. 5 and 11. A preferred shim
design is shown in detail in FIG. 11B. The ribbon of film
preferably meets the target surface at a distance of between 5 and
15 mm from the honor edge of the die 10. i.e., where the opposite
sides of the ribbon have become essentially parallel.
Block 28 has locator holes 41 which receive the guide pins 40 and
locate the block relative to the face 42 of the opposing block 23,
as well as the hidden face of the spacer 26. Block 28 has a single
horizontal gallery groove 50 which is opposite but co-extensive
with the groove 38 within the relief 44 of the spacer 26 to allow
the horizontal fluid chamber created by the two grooves 38, 50 to
fill with the PVA material while preventing lateral outflow as well
as upflow between the spacer and the inside surface 41 of the block
23. An aperture 56 cooperates with the valve 30 to pull the pin 61
out of the flow chamber when cutoff is desired. This rapidly
increases chamber volume and correspondingly reduces chamber
pressure, resulting in a slight negative pressure with material
pull-back. This feature is optional.
When applied to a fully finished painted surface for temporary
protective purposes, the material applied is polyvinyl acetate in
an emulsion containing, for example, about 50% water and 50%
polymer. When dispensed, the material is extruded from the
applicator die 10 with a width of about 85 mm. Thereafter, it has
been found that the material begins to converge due to surface
tension. Accordingly, the spacing between the outlet 58 of the
applicator die 10 and the surface upon which the ribbons are being
applied is preferably held such that the material is applied at or
near the point of maximum width where the opposite edges are
parallel. See FIG. 7.
As indicated above, the applicator die 10 can be moved at the
selected rate over the target surfaces while material is dispersed
or extruded therefrom. When placed in an infrared oven, drying time
of about 15 minutes has been shown to be possible at a temperature
of 180.degree.. Convective and/or microwave drying can also be
used.
It will be noted that the applicator die 10 is operated in a
position which is orthogonal to the target surface rather than
angled or tipped in the direction of flow as is the case with
typical spray-type, deflective applicators. It will also be noted
that the extruded ribbon of material being applied is not particled
or atomized; rather, it is a full, continuous film of material
moving outwardly and downwardly in laminar form and at a desired
rate. Because the applicator is ambidextrous, it does not have to
be turned around by rotation between parallel passes in opposite
directions and this too, increases the rate at which an automobile
body part, for example, a hood, can be covered. After coating, the
component goes to an oven for faster curing. FIG. 7A shows how the
film behaves as it leaves the applicator die 10. Because of the
diverging or flared shape of the die exit slot, the ribbon diverges
at 53 but quickly converges due to surface tension. The
die-to-target spacing is preferably such as to apply the ribbon to
the target surface at about the point of maximum ribbon width.
FIG. 7B shows how the extruded material behaves when using a
straight sided spacer 26' to define the die outlet slot 59 with
edges A5. The material converges immediately upon departing the
edges A5 due to surface tension; see ribbon edges 53, and becomes
difficult to control.
FIG. 7C shows in profile two ribbons that can be created using the
dies of FIGS. 7A and 7B. The top ribbon A-8 is 300 microns thick
and has 500 micron thick edge beads, measured at a distance of 10
mm from the die outlet. This is undesirable.
The bottom ribbon A-7 shows the ribbon profile produced by the
invention die of FIGS. 5 and 11B. It is 200 microns thick with 250
micron edge beads at 10 mm from the slot outlet. This is the
desirable profile. The very shallow edge beads promote clean
peeling without excess material in the overlap areas or along the
edges of the anti-chip coat.
FIG. 8 is a schematic diagram of a method of applying a protective
film of an automobile. The first step 100 as indicated by the
legend is to apply the emulsion in overlapping and alternating
strokes. The second step 102 is to dry the emulsion with infrared
radiation. The third step 104, in the case of a manufactured
automobile, is to ship the protected vehicle and the final step
106, typically performed by the dealer, is to peel the coating off
of the vehicle and dispose of it in an environmentally appropriate
fashion. It peels in one piece and the material can be
recycled.
An alternative or additional method of using the applicator die 10
is shown in FIGS. 4 and 9. This method comprises a first step 200
of applying primer to a rocker panel of an automotive body 300 in
conventional fashion. Thereafter, a robot 302 carrying an
applicator die 10 essentially as shown in FIGS. 5 and 6 and
described above is used in step 202 to apply a PVC emulsion to the
primed rocker panel as an anti-chip coating. It will be understood
that the applicator die 10 has material and coolant supply lines
running to it as is the case for the film applicator in FIG. 1. In
this case, the polyvinyl chloride solution or emulsion comprises a
polymer in an organic solvent applied in a ribbon of the
appropriate thickness while the rocker panel is essentially
vertical. Temperatures, spacing and application rates are
empirically determined in view of the fact that the material has a
viscosity of about 50,000 centipoise. It has been found that
additional primer and body color paint can be applied over the PVC
ribbon in step 204 before it is dried; i.e., paint can be applied
"wet-on-wet." The PVC surface produced by the applicator is glossy
and uniform in thickness. In this embodiment, only one pass along
the rocker panel is required.
There are numerous advantages to the use of this process for the
anti-chip coating relative to the prior art process of spraying the
coating on the car. Spraying requires the entire vehicle to be
masked to protect it against overspray which is highly detrimental
to paint finishes. Therefore, this method eliminates the need to
mask the vehicle and to remove and dispose of the masking
materials. In addition, the laminarized ribbon offers a smooth,
glossy appearance as compared to the rough appearance caused by
spraying.
FIGS. 11A and 11B show the preferred embodiment 88 of the extrusion
die and especially the geometry of the relief 44 in the shim 26
relative to the groove 38 and the 180.degree. rounded ends A-1
thereof. FIGS. 11.A shows the shim 26 overlying the die block 28
with the top edge 300 of the shim relief overlying and coextensive
with the top edge of the gallery groove 38. The right and left
corner or inside edges 46 and 48 of the shim partially follow the
curve of the gallery groove end, but flare downward to points TP
which are located at the 36 degree point along the arc of the outer
die block 28 corner radius. Both the right and left inside edge
lines 46 and 48 of the shim, which begin at the outer radius point
TP, terminate where they intersect the tangent of the half-circle
(A-1) of the right and left ends of gallery groove 38. The right
and left end-points of the shim at TP define the endpoints of the
extrusion slot which will therefore determine the width of the
ribbon as it emits from the slot. In FIG. 11B, the gallery groove
radius (A-1) and the outer die block corner radius at point TP
share the same centers of curvature 59. Therefore, the internal
extrusion slot surface distance 57 over which the material exiting
the die flows in contact with the slot surfaces 58 is constant from
gallery edge to outlet edge, including the curved portions at the
right and left ends of the slot which arc upward to the 36 degree
endpoint of the slot, as terminated by the edge 86 of the shim.
This allows a uniform velocity of material emitting from the slot
outlet face A-9 on the die block from ribbon edge to edge, all
across the width of the slot. The ribbon trajectories will emit at
an angle normal (perpendicular) to the slot face A-9 of the die
block, which means that ribbon trajectories emitting at any point
along the straight segment of the slot will all be parallel, but in
the curved ends of the slot at the right and left corners of the
die block, the trajectories will gradually diverge from zero
degrees to 36 degrees at the right and left slot end-points at TP.
This enables the outer right and left edges of the material ribbon
53 to exit the die slot at a trajectory 36 degrees from the
centerline of the ribbon. Immediately as the ribbon emerges and
flows out from the slot however in FIG. 7, the inherent surface
tension A6 of the ribbon material will pull across the ribbon width
to gradually arc the right and left edge trajectories inward toward
each other an angle at first parallel or zero degrees) to the
centerline of the ribbon, and then will continue to arc inward to a
final trajectory having a negative angle to the centerline of the
ribbon (about -20 degrees). If allowed to continue, both ribbon
edges would finally intersect and the ribbon would undesirably
coalesce into a rod or cylinder of free-flowing material, instead
of a ribbon.
The zone of the emerging ribbon where the right and left ribbon
edges are substantially parallel to the ribbon centerline at A-2,
is designated the "zone of controlled film width and thickness"
A-3, which is where the process of this disclosure is carried out.
This sector of the ribbon extrusion, which is generally 5 to 15 mm
from the face of the die block, has a substantially uniform
edge-to-edge width (about 85 mm wide in this embodiment) and a
constant film thickness of about 0.2 mm or 200 microns edge to
edge. This ribbon zone of 5 to 15 mm from the slot face of the
applicator, therefore defines the ideal range of distance (same
5-15 mm) for the applicator to dispense an optimum ribbon shape
onto a surface. For this reason, robotic motion for dispensing
ribbons is programmed such that the slot face of the applicator is
taught a nominal 10 mm distance from the substrate surface. This
will produce a wet ribbon extrusion on the substrate surface which
will be of uniform width (85 mm, plus or minus 1 mm) and of uniform
wet film thickness (0.2 mm). The only variance in wet film
thickness across the width of the ribbon, are found at the edges,
for no more than 1 mm inside the ribbon edge, where the wet
material thickness is measured to be about 0.25 mm. (A-7 in FIG.
7C), This increased thickness (0.05 mm) which occurs within a
millimeter from the right and left edges of the ribbon, is an
advantage which enhances the peelability of the dry film when it is
removed from the car body. Conversely, ribbon edges which are
tapered under the 0.2 mm wet film thickness are a detriment in this
application, since the tensile strength of the thinner film will be
weaker than the adhesive strength holding the dry film to the
substrate, and the dry film will tear at the edges during removal,
leaving troublesome lines of dried film residue along the perimeter
boundary of the ribbon pattern on the car body.
FIG. 7B shows the ribbon edge profile A4 produced by conventional
extrusion means which are considered prior art, where the shim is
trimmed at A5 (instead of at 46) which is at the right and left
termini of the straight segment of the slot. This is a
straightforward design which insures that all points of the ribbon
emerging from the straight slot face are at the same velocity and
in a parallel trajectory normal to (or perpendicular to) the slot
face. Often, and especially with higher viscosity materials like
clays and ductile metals, this will produce a ribbon of material
having the same extruded width as the slot opening width of the die
block. In the case of polymer emulsions however, which are
relatively low viscosity liquids, the force of surface tension A6
in the liquid ribbon shape as it emerges from the die slot will
immediately draw the ribbon edges together A4 as described above.
This ribbon produced from the conventional design will have no
parallel edges A2 for creating a "zone of controlled width and
thickness" and can only emit a ribbon of constant width ribbon
length and thickness at a distance no more than 1 mm from the die
face A-9. The consequence of robotically applying transit coating
from a die block only 1 mm from the carbody surface is impractical
and dangerous and therefore unfeasible. Applying a transit coating
emulsion with this conventional die block design at the standard 10
mm distance (as used in the invention) would produce a narrower
ribbon where the overall thickness of the ribbon will be greater
than the specified 0.25 mm limit, and the ribbon edges will have
grown considerably to 0.5 mm thick for a width of 3 mm or more (see
A-8, FIG. 7B), will propagate drips and runs, and require
considerably longer drying times for the thicker edge portions,
which would also be unfeasible in production.
FIG. 11B shows the exit trajectory of the ribbon edge at TP aligned
with the internal flow trajectory of the material 55 passing across
the surface distance 57. The angle of flow trajectory 55 is defined
by two points on this line: the radius center point 59, and the
shim termination point at TP. This line of trajectory (shown in
this embodiment as 36 degrees from centerline) is also the shortest
flow path for the material travelling across the slot distance 57,
which will pass by the shim terminus at point TP to form the edge
of the ribbon when it exits the slot. The difference between the 36
degree flow trajectory angle at the end of the slot, and the angle
of the shim edge 46 creates a triangular area 49 within the outlet
slot where comparatively little material flow takes place. The
triangular area 49 does however create an area of "laminar relief"
adjacent to the flow path of the material which will form the edge
of the ribbon. This feature of the triangular area 49 containing
material adjacent the main flow path for the ribbon edge
contributes less resistance to the flow path than if the shim edge
46 were aligned directly along that path way at a 36 degree angle.
When the shim edges at 46 are aligned with the 36'' degree material
path, they present a hard boundary adjacent to material flow across
the slot distance 57, which slows the ribbon velocity at the edges
when emerging from the slot face, causing increased thickness of
the ribbon edge (>0.3 mm or 300 microns)when dispensed on the
substrate surface, which is undesirable. The laminar relief created
by area 49 creates less boundary impedance and consequently higher
velocity for the adjacent faster-flowing material which will form
the ribbon edge when it exits the slot, and thereby produces the
ideal ribbon edge thickness (0.25 mm) on the substrate.
The ribbon edge exit angle which is controlled by the shim edge 46
and endpoint 47 were optimized at 36 degrees in the present
embodiment to create the optimum "zone of controlled film width and
thickness" for transit coating material application, and this was
determined from observation and experimentation. However, other
polymer emulsion formulas for other types of application, which may
have a lower or higher viscosity, and/or a greater or lesser ribbon
thickness requirement, may require a greater or lesser ribbon edge
exit angle to optimize the zone of controlled width and thickness
for that material and application. For this reason the active range
of this invention for the possible exit angles of the ribbon edge
which will produce the optimized zone of controlled width and
thickness will lie between 5 degrees and 50 degrees relative to the
applicator centerline. Likewise, although the width of the ribbon
of the present embodiment is 85 mm, the straight segment of the
applicator gallery and slot can be elongated considerably while
preserving the radiused slot endpoint geometry to produce ribbon
widths of 200 mm or even wider, or narrower ribbon widths could be
produced by shortening the straight slot segment down to a ribbon
width of about 25 mm. The scalability of ribbon width (25 mm or
greater), and the range of viable ribbon edge exit angles (5 to 50
degrees) are inherent to the invention.
FIG. 10 is a schematic diagram of a representative system, in this
case, for the application of the PVA film as a protective coating.
However, the essentials of the system are the same for all
applications. As shown in the drawing, material is supplied from
drums 60, 62 through lines 64 and 66 which are connected into a Y
conduit 68 and from there through parallel legs 70, 72 with drains.
Conduit 74 flows from the leg 72 through a filter 76 and from there
into a heat exchanger 78 which is controlled by a temperature
controller 82. Finally, the material flows into the conduits 80
which supply the applicator die 10. Adjacent the applicator die 10
in a standby position is a liquid-filled cleaning standby station
84 with an interior brush which can be activated as necessary. The
fluid in the case of the aqueous PVA emulsion is water. Next to the
cleaning standby station 84 is a cleaning station 87 where the
applicator can be blow-dried. A purge station 90 may be used where
desired.
Summarizing, the applicator die 10 uniquely dispenses a ribbon of
material of uniform thickness at a controlled speed and with
improved edge control. PVA in a water emulsion is used in the
protective film application process of FIG. 8 or for masking. PVC
in an organic emulsion is used for the anti-chip coating. The two
examples demonstrate that the film ribbons can be applied to
horizontal as well as vertical surfaces. They can also be applied
to inverted and curved surfaces. Although a shim between the two
body parts is shown, the objective is to shape the die outlet slot
so that the side and bottom edges are such that (a) the film ribbon
flares outwardly at about 36.degree. and (b) the distance the film
travels from the center of the gallery grooves to the bottom edge
of the slot is constant across the slot width; i.e., from left
radiused edge to the right radiused edge, thereby promoting a
constant exiting film velocity across the ribbon.
While the invention has been described in connection with what is
presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiments but, on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims, which
scope is to be accorded the broadest interpretation so as to
encompass all such modifications and equivalent structures as is
permitted under the law.
* * * * *